From: Jim Weirich <jweirich@...>
Date: 2003-03-25T20:47:26+09:00
Subject: Re: Iterate over two lists in parallel

On Tue, 2003-03-25 at 02:22, Hal E. Fulton wrote:

> I'd really rather use the object itself to 
> iterate, even if I must initialize it.
> 
> Something like:
> 
>   x = [5,6,7,8,9]
>   x.reset
>   loop do
>     a = x.get
>     # ...
>   end
> 
> C'est possible?

It is possible to do it this way.  In fact, Bertrand Meyer likes this
style in that his Eiffel library defines his iterators as part of the
collection object.  I've never liked it though.  Consider the following
...

   def outer_function
     stuff.reset
     while stuff.more?
       inner_function(stuff)
     end
   end

   def inner_function(list)
     list.reset         # Oops ... we just blew away the iteration
     while list.more?   # in the outer function
       do_somthing
     end
   end

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)